This invention relates generally to feeder units for use in weighing systems and more specifically relates to a new and novel flow control system and method for single briquette delivery to a weighing device to secure accuracy in weighing of the charge in the system.
In the weighing of commodities, it is a customary practice to use a sensitive weight sensing unit in combination with a product delivery system that provides a uniform flow rate. The final weight is anticipated in the cut off of product flow and because the flow is uniform, the desired accurate weights can be secured. This has not been true in weighing briquettes such as charcoal, sugar or the like. For example, the most accurate weighing of granular sugar would be plus or minus one grain of sugar which is commercially not possible nor economically feasible since the briquette weighing one ounce is the smallest particle being weighed. The most accurate weighing at plus or minus one briquette is economically desirable and heretofore has not been possible with prior art weighing systems.
Most weighing systems of the prior art designs employ a two-stage product delivery with a bulk delivery feeder being utilized for 90 to 95 percent of the weight desired and a fine or dribble feeder being utilized for the final 5 to 10 percent of the desired weight in order to attain the desired accuracy.
In the control of the fine or dribble feed of the system, a level control has been utilized to restrain the flow of excess briquettes in the dribble feeder tray. It is known in the art to use fixed wiper plates at right angles to and across the flow path to restrain the flow of briquettes and provide a desirable level of briquettes in the dribble tray. The prior art level controls were generally fixed or vertically adjustable at some desired position over the dribble feeder tray at right angles to the flow and this arrangement may have been modified by one of rubber or some other flexible material or skirt on the bottom of the wiper plates in an attempt to prevent wedging of the objects beneath and behind the wiper plates. When such wedging occurred, the bulk object had no place to go, and the entire system had to be shut down in order to free the jammed bulk object from beneath the door in order to continue the weighing and packaging of the commodity. Such jamming and stopping of the system resulted in costly downtimes and extremely slow packaging speeds. The applicant's new and novel invention is directed primarily to the elimination of the jamming in the dribble feeder portion of a weighing system.